Myocardial edema will be produced in arrested rabbit hearts. Increases in diastolic stiffness will be measured as a function of the increase in ventricular wall thickness due to edema. Preliminary experiments show that both (1) edema and (2) diastolic compliance changes originally produced by hypoosmolar coronary perfusion in the arrested rabbit heart can be reversed by later perfusion with hypersmolar potassium-glucose-adenosine solution with added dextran. Preliminary work has also included the development of a mathematical model based on the principles of solid mechanics to explain the observed ventricular compliance changes in cardiac edema. The proposed work is aimed at understanding the quantitative relation between (reversible) changes in myocardial edema and passive stiffness changes. These studies are therefore closely relevant to the mechanisms by which the coronary perfusion of myocardial protection agents may change myocardial water content and therefore cardiac performance.